The speech also came in the context of Labour Friends of Israel chairwoman Joan Ryan - a prominent critic of the leadership’s handling of the anti-Semitism row - and Luton South MP Gavin Shuker losing local no confidence votes on Thursday.

Mr Umunna said: “There is now a clear and present danger that this tradition is driven out of our party.

“Having only been re-elected by their constituents last year, already centre-left MPs are being targeted systematically with motions against them for standing up for these values - for demanding we have a zero tolerance of racism in our party.

“More motions such as this are expected by colleagues. My message to our leadership: it is within your power to stop this so call off the dogs and get on with what my constituency, one of the most diverse communities in the nation, demands we do - without equivocation, fight this Tory Brexit.”

However, Mr McDonnell told Sky News: “There are no dogs being called on. I actually think referring to our party members as dogs is just unacceptable.”

It was “an appalling expression to be used about Labour Party members”, he added.

He said “of course there isn’t” a purge but “individual constituencies, if they are dissatisfied with what their local MP has done or said or voted, they will raise their concerns in the traditional way which is a vote of confidence or no confidence, or even just around a particular issue”.